STAINING OF SPORES. 137 



prepare the cover-slips in the ordinary way, thpn cover 

 the layer of bacteria upon them with glacial acetic acid, 

 which is instantly poured off (not washed off in water), 

 and the aniline-water gentian-violet solution dropped 

 upon them ; this is allowed to remain three or four 

 minutes, is poured off, and a few drops more are added, 

 and lastly the slip is washed off in water. A very clear, 

 sharply-cut picture usually follows this method of pro- 

 cedure. 



Staining of Spores. — We have learned that one of 

 the points by which spores may be recognized is their 

 refusal to take up staining substances when applied in 

 the ordinary way. They may, however, be stained by 

 special methods ; of these one that has given very satis- 

 factory results in our hands is as follows : The cover- 

 slip is to be prepared from the material containing the 

 spores in the ordinary way, dried, and fixed. It is then 

 to be held by its edge with the forceps, and its surface 

 covered with Loffler's alkaline methylene-blue solu- 

 tion. It is then held over the Bunsen flame until the 

 fluid boils ; it is then removed, and after a few seconds 

 is heated again. This is continued for about one 

 minute, after which it is washed off in water and 

 dipped five or six times in alcohol containing about 0.2 

 to 0.3 per cent, of hydrochloric acid. This is rinsed off 

 in water and the preparation is now stained for from 

 eight to ten seconds in aniline-water fuchsin solution 

 (Koch-Ehrlich solution), and finally again washed in 

 water. By this method the spores are of a blue color 

 and the body of the cell red. 



By another process the cover-slip is floated, bacteria 

 down, upon the surface of a watch-crystalful of freshly 

 prepared Koch-Ehrlich solution of fuchsin. This is 



